The invention relates to a device for monitoring the flow of a substantially direct current in a load and a method for the implementation of this device.
In certain applications, for example in aeronautics, the flow of current in a load is monitored, in order to activate an alarm if there is no current.
When the load is powered by a DC voltage source, a means can be placed on one of the power supply wires of the load to detect the flow of a current in the power supply wire of the load. If this means indicates the absence of current, it can be deduced that the power supply is absent and that the load has an operational defect. In practice, the known means used to detect the flow of a direct current, such as a Hall effect detector, require an amplifier to process the signal coming from the detector. Such an amplifier too could have an anomaly and could, for example, get blocked in a state in which it would permanently indicate the flow of a current in the load regardless of the actual existence of current flowing in the load. The monitoring device can be monitored by providing for a second monitoring device to monitor the first one This complicates the general making of the system which comprises the direct current supply, the load and the two monitoring devices.
The invention is aimed at overcoming this problem by proposing a monitoring device which, even if there is a malfunctioning of the device, will indicate an anomaly and, unlike the case of the solution considered here above, will not be able to indicate efficient operation when no current is flowing in the load.
To attain this goal, an object of the invention is a device for monitoring the flow of a substantially direct current in a load, characterized in that it comprises, connected in series with the load, first means to detect the presence of an alternating current and in that it furthermore comprises second means to interrupt the current flowing in the first means while maintaining the current in a substantially direct state in the load.
An object of the invention is also a method for monitoring the flow of a substantially direct current in a load characterized in that the method uses a device comprising, series-connected with the load, first means to detect the presence of an alternating current, second means to interrupt the current flowing in the first means as well as third means capable of short-circuiting the first and second means and in that the method gives rise gives rise, cyclically, to the sequencing of the following stages of operation so long as the load is powered:
during the first stage, the current flows only in the second means;
during the second stage, this current flows both in the second means and in the third means;
during the third stage, the current flows only in the third means;
the fourth stage is identical to the second stage.
The existence of the second and fourth stages prevents the current from being interrupted in the load. Indeed, the opening and closing of electronic switches to block the current or make it flow in the second and third means are never perfect. In the absence of the third and fourth stages, this risks causing electromagnetic disturbances due to fluctuations in the flow of the current.
Advantageously, an object of the invention is a device for the monitoring of the flow of a substantially direct current in a load, characterized in that it comprises at least one first electronic switch series-connected with the load and first means to detect the presence of an alternating current, the first electronic switch being controlled so as to set up the alternating current in the first means and in that it furthermore comprises second means to keep the current in a substantially direct state in the load.
One method of implementing this device consists in opening and closing the electronic switch cyclically while at the same time making the second means operable and inoperable, also cyclically, to keep the current in a substantially direct state in the load and let the current flowing in the load pass through the second means only periodically.
According to a first embodiment, the method of the invention is characterized in that the second means comprise a first electronic switch, in that the third means comprise a second electronic switch parallel-connected to an assembly formed by the first electronic switch and the first means to detect the presence of an alternating current, and in that the method gives rise, cyclically, to the sequencing of the following stages of operation so long as the load is powered:
during the first stage, the first electronic switch is closed and the second electronic switch is open;
during the second stage, the first and second electronic switches are both closed;
during the third stage, the first electronic switch is open and the second electronic switch is closed;
the fourth stage is identical to the second stage.
According to a second embodiment, the method according to the invention is characterized in that the second and third means comprise four electronic switches, in that the first switch and the fourth switch are both series-connected with the load, in that the third switch and the second switch are both series-connected and form an assembly parallel-connected with the first and fourth switches, in that the common point of the first and fourth switches is connected to the common point of the third and second switches, and in that the first means to detect the presence of an alternating current monitor the current flowing between the two common points and in that the method gives rise, cyclically, to the sequencing of the following stages of operation so long as the load is powered:
during the first stage, the first and second electronic switches are conductive and the third and fourth electronic switches are non-conductive;
during the second stage, all four electronic switches are conductive;
during the third stage, the first and second electronic switches are non-conductive and the third and fourth electronic switches are conductive;
during the fourth stage, all four electronic switches are conductive.